Clotfelter, Ladd, and Vigdor 671
with a regular license. Though this finding may reflect in part the training that lateral entrants receive during the two years of their license, it also reflects selection. Lateral
entrants have high departure rates, and it is reasonable to assume that the ones who remain in teaching are more effective than those who depart. The students in our
most recent sample cohort were taught by 804 lateral entrants, but by only 155 former lateral entrants.
25
Students taught by teachers with “other” licenses have average test scores even further below those in the base category, but the coefficient
does not differ from that for lateral entrants at standard levels of significance.
E. Certification by subject area
A second component of the licensing requirement is that teachers be certified by subject area. For the time period covered in this study, such certification required
that a teacher both successfully complete an approved program of study in the sub- ject area and earn passing grades on the appropriate Praxis II tests.
26
Table 4 shows the effects of certification by subject where results are aggregated across the five subject areas.
27
The coefficients 0.07 and 0.05, which are statistically distinct, indicate that being taught by a teacher who is certified in the subject she is
teaching or in a related subject leads to higher test scores, and that the effects are large relative to those for the other teacher credentials. The estimated effects of
certification, for example, are many times the size of those that are implied by a one standard deviation difference in test scores. We note, however, that the estimates
are relative to a small group of teachers who are not certified.
These certification results are disaggregated by subject area in columns II and III of Table 5. The entries in these columns shed light on whether being certified in
math contributes more to student achievement in algebra or geometry, for example, than does being certified in biology to achievement in biology. The entries in the
two columns differ in that those in column III are based on models that also include subject-specific test scores. The similarity in the results across specifications high-
lights the fact that the subject-specific test scores, measured as continuous variables, exert effects on student achievement that are quite independent of that due to cer-
tification.
As was the case for the test score variable, the results for teachers of the two math courses, algebra and geometry, stand out. Being certified in math increases the
achievement of a teacher’s students in a math course on average by about 0.11
25. The 804 lateral entrants were distributed by subject as follows: 226 in algebra, 195 in biology, 132 in ELP, 164 in English, and 87 in geometry.
26. In part because of the high pass rates on the PRAXIS tests for those teachers who successfully complete the required programs of study, the state has recently dropped the PRAXIS II tests for those teachers. In
addition, it is now the case that a teacher who is already licensed in one area can become certified in another based on passing scores on the relevant PRAXIS tests alone.
27. These certification results, and also the subject-specific certification results in Table 5, are based on a relatively broad definition of certification. For example, certification in general science is included in the
definition of certification for biology. The results in Table 4 are qualitatively similar when we use a stricter definition that would, for example, count general science as a related subject for biology. In the subject
specific variations reported in Table 5, large standard errors make it impossible for us to sort out the effects of certification in the actual subject from those in a related subject.
672 The Journal of Human Resources
standard deviations. This finding for math is fully consistent with earlier studies by Monk 1994 and Monk and King 1994 who find, using national survey data, that
teacher preparation in math has positive effects on student test scores in math. The only other subject for which certification matters is English, where once again the
estimated effects are large.
F. National Board Certification
